Enhanced catalytic activity and magnetization of encapsulated nickel Schiff-base complexes in zeolite-Y: a correlation with the adopted non-planar geometry

Abstract

Square planar Ni(ii)-Schiff base complexes when encapsulated in a supercage of zeolite Y have shown altered optical, magnetic properties and catalytic activities in comparison to their corresponding free states. Different characterization techniques like XRD analysis, SEM-EDX, AAS, FTIR, UV-Visible spectroscopy and magnetic studies as well as detailed theoretical studies altogether show the differences in the properties of complexes in free and encapsulated states. All these studies have suggested that the largest complex deviates by the maximum amount from its free-state properties and a fascinating correlation between the extent of deviation from molecular dimension and modified catalytic activity of encapsulated complexes is observed.

The functionality of the hybrid systems driven by molecular dimension of the guest copper Schiff‐base complexes entrapped in Zeolite‐Y

“…Largest complex experiences more distortion and shows the most enhanced catalytic activity for styrene oxidation after the encapsulation. Interestingly, this complex is least reactive for the same catalytic process in its free state . In the present study, the parallel behavior of zeolite Y encapsulated copper salen complexes is observed for the oxidation of styrene in presence of H 2 O 2 .…”

“…It is quite interesting to perceive a regular blue shift and intensification of the d‐d transitions in the encapsulated copper ‐ Schiff‐base complexes. Such behavior already has been observed in the zeolite Y encapsulated complexes . Observed modified electronic behavior in the d‐d region is certainly an effect of different geometry of the co‐ordination sphere, which the guest complex has adopted under the space restrictions of host supercage.…”

“…C (1 s) signals in the free state CuS1 complex appear at 283.35 and 285.03 eV, which corresponds to the sp 2 and sp 3 carbon atoms respectively . N (1 s) peaks for the complex are observed at binding energies 397.68 eV (M‐N) and 399.61 eV (C=N) whereas O (1 s) peaks appear at the binding energies of 531.26 eV (M‐O) and 533.74 eV (C‐O) . These XPS peaks are observed at almost identical binding energies for the encapsulated complexes.…”

“…The equivalent XPS signals for CuSp1–Y complex are also observed at their corresponding binding energies; for the C (1 s), signals have appeared at 284.13, 285.41 eV, whereas N(1 s) and O (1 s) signals are observed at 399.18, 401.65 eV and 530.66, 532.88 eV respectively. Furthermore, both the encapsulated complexes have shown zeolitic Na(1 s), Al(2p) and Si(2p) XPS signals at their respective positions (XPS spectra are presented in supporting information Figure S7‐S9). Comparative XPS binding energy data of both free and encapsulated complexes, as well as higher shifts in binding energy for the Cu 2p 3/2 and Cu 2p 1/2 peaks in both encapsulated complexes, essentially signify the encapsulation of metal complexes inside the zeolite Y.…”

“…have observed that the copper and cobalt complexes are more reactive catalysts compared to the its corresponding nickel complexes for the selective oxidation of phenol by using H 2 O 2 as the oxidant . It is quite clear that the encapsulated complexes in zeolite Y are competent catalysts for oxidation of hydrocarbons, and most of the studies have suggested that enhanced activity of the encapsulated complex is definitely a consequence of the distorted geometry of the complex under space constraint inside the rigid cavity . Already the diverse effects of different substituents on the structure and functionality of the copper Schiff‐base complexes are discussed thoroughly .…”